1. Field of the Invention
This invention generally relates to water heaters, and more specifically, a portable temperature-controlled water heater.
2. Prior Art
Outdoor sports enthusiasts many times enjoy aspects of nature requiring a separation from modern amenities such as running water, hot showers, and many of the conveniences that are typically encountered during day-to-day living. Though these accommodations may be desired, they are generally not practical to employ in the outdoors.
A very basic method of heating water with a kettle over a fire or camp stove, though simple, is relatively inefficient in producing water in quantities sufficient for showering. In addition, it is difficult to obtain a precise water temperature suitable for contact with skin.
U.S. Pat. No. 6,877,461 to Long et al. (2005) discloses a method for heating water by mechanically pumping water through a heat exchanger warmed by a burner assembly. This method requires the transportation of bulky equipment, a supply of batteries, and fuel weighing upwards of 12 kg (26.4 lbs) or more.
A thermosiphon water heating system disclosed in U.S. Pat. No. 5,417,201 to Thomas et al. (1995) relies on density changes that occur as water is heated within a heat exchanger. The change in water density motivates the circulation of water through the heat exchanger. A single container of water is gradually heated taking a considerable amount of time, upwards of an hour or more. The user must monitor the water temperature in the container and judge when the time is right to remove the heat exchanger from the heat source. In addition, due to the nature of the thermosiphoning principle, stratifications in water temperature prevail vertically within the water container. During operation, the water towards the top of the container is likely to be as much as +10 C (+20° F.) warmer than the water on the bottom making it difficult to determine average bulk water temperature.
Other portable water heaters such as those disclosed in U.S. Pat. No. 5,460,161 to Englehart et al. (1995) and U.S. Pat. No. 3,246,644 to Peterson (1966) heat water to the boiling point within a heat exchanger. Upon boiling, water expands into steam driving the flow of water through the system similar to an automatic coffee maker. Water and steam temperatures up to 100 C (212° F.) can pose additional handling risks for the user during normal operation. Also, from a thermodynamic perspective, it is less efficient to heat water to the boiling point only to have to dilute or cool the water down to approximately 38 C (100° F.), necessary for contact with the skin. Heat energy is spent during the phase change of water from a liquid to a gas.